The Republican senator John McCain yesterday renewed criticism of Barack Obama's foreign policy, accusing him of being soft on Cuba by proposing to hold talks with Raúl Castro and ease the US embargo.

After last week's depiction by George Bush and McCain of Obama as an appeaser of Iran, McCain took up the theme again in a speech in Miami, home to many Cuban exiles, accusing the Democratic presidential candidate of sending "the worst possible signal" to its leaders.

By contrast, McCain said that as president he would maintain the US embargo on Cuba and ask the justice department to aggressively pursue Cuban officials.

Bush, who tightened the embargo in 2003, is expected to reinforce McCain in a speech on Cuba today. It marks the second time in a week, after Bush's emotive speech about appeasement at Israel's Knesset, that the sitting president and Republican presidential hopeful have taken up the same foreign policy debates.

McCain's speech on Cuba also represents the opening of the battle for the swing state of Florida in the presidential election. Cuban-Americans have been among the Republican party's most reliable supporters, but a younger US-born generation is not as consumed with the struggle against Fidel and Raúl Castro as their parents.

Obama begins a three-day swing through Florida today. Hillary Clinton also visits Florida today. Obama's campaign team will welcome the foreign policy debate, partly because it shifts the focus to the McCain-Obama battle in November and away from the dying days of the Obama-Clinton battle for the Democratic nomination.

Obama's campaign team believe foreign policy can be positive for them, particularly over Iraq, but also because it reinforces their argument that McCain would be a continuation of the Bush presidency.

The theme was taken up yesterday by Senator Chris Dodd, an Obama supporter, who accused McCain of inconsistency for having favoured, in the past, negotiations with Cuba to lift the embargo but now taking a hard line, "embracing a policy that has failed the Cuban people and the American people alike for 50 years".

Obama has also been accused of inconsistency on Cuba because of his resistance to expanding travel and cultural exchanges.

McCain, speaking to an audience in Florida, promised he would not passively wait for an end to its tyranny. "I wish the other presidential candidates felt similarly," he said.

McCain said Obama's support for lifting the embargo and his offer to talk to Raúl Castro "would send the worst possible signal to Cuba's dictators - there is no need to undertake fundamental reforms, they can simply wait for a unilateral change in US policy. I believe we should give hope to the Cuban people, not to the Castro regime."

The Republican presidential hopeful said that the embargo had to stay in place until basic democratic rights were in place, and promised his administration would take a tougher approach to the Cuban government, working to prosecute Cuban officials implicated in murder, drug-trafficking and other crimes.